Does higher nutrient availability reduce drought resistance in grassland species? - Insights from a global change experiment

Carola Kiene1, Leonor Álvarez-Cansino1, Eunyoung Jung1, Bettina Engelbrecht1
1 Functional and Tropical Plant Ecology, University of Bayreuth

O 1.6 in Plant and soil responses to drought: Interdisciplinary approaches and views

10.10.2019, 12:30-12:45, H36, NW III

Drought and nutrients, two of the main global change drivers, are important factors shaping community composition, biodiversity and ecosystem function in grasslands. Although it is suggested that communities in high nutrient sites are less drought resistant, interactions of nutrients and drought are complex and of­ten contradictory, suggesting that the effect of nutrients on drought respons­es differs across species. Thus, our ability to predict consequences for grassland agriculture and natural grasslands under climate change remains severely limit­ed. In this study we comparatively assessed the effect of different nutrient con­ditions on whole-plant drought responses of 13 common temperate grassland species. In a common garden experiment, species were grown under four dif­ferent nutrient conditions (unfertilized control, nitrogen (N) or phosphorous (P) addition, and combined addition (N+ P)) in mesocosms. In the second grow­ing season, half of the plants were exposed to an extreme drought. Species in­creased their biomass under nutrient addition, especially under the combined addition of N and P. Drought reduced growth in all species, but this reduction was parallel to the positive response of the species to fertilization (no drought-nutrient interaction). Thus, plants in the N+P treatment had the highest biomass even under drought.  In general, drought mortality averaged around 10%, with small differences between nutrient conditions for most species. Accordingly, a wide range of common temperate grassland species possess high drought resistance, regardless of nutrient availability. Especially, species associated with moist habitats (Ellenberg indicator values) were more drought sensitive.These responses will likely lead to changes in community structure and may seriously affect the produc­tivity (i.e. agricultural value) of grasslands with increasing drought under global change.

Keywords: Global change, drought, fertilizer, land-use, common garden experiment, Ellenberg indicator values, drought resistance

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